Meta illuminator

ABSTRACT

An illuminator with a metalayer for redirecting light in a desired far-field radiation pattern by using subwavelength posts.

CROSS-REFERENCE TO RELATED APPLICATION

This patent application claims the benefit of U.S. Provisional Patent Application No. 62/440,428, filed Nov. 10, 2016, and titled INFRARED ILLUMINATORS, CAMERAS, AND BIOMETRIC DETECTION AND LOGIN SYSTEMS, and which is incorporated herein for all purposes.

BACKGROUND

Projectors or illuminators are often used to project infra-red light (about 700 to 2500 nm wavelength for near-infra-red (NIR) onto an object and then use a sensor (or camera) to detect the light reflecting from the object in order to form images of the object. The images then may be used for a number of applications including biometric detection for security authorization purposes such as with face detection or iris scanning recognition. These detection systems may be used to authorize a user to unlock many different objects such as physical doors, computers, computer files, or other electronic devices to name a few examples. Such NIR systems also may be used for eye tracking and other object detection operations such as with motion detection related-games or artificial intelligence (AI), computer vision, and so forth. In these systems, the sensed reflections from the NIR illuminator are used to form an IR or NIR image with specific characteristics needed to perform the desired detection or to use the image for other applications. The cameras that generate images of a user's face to use the image to authorize access to something may be referred to herein as a face login camera.

The conventional NIR illuminator devices use LED illuminators. These conventional illuminators, however, often suffer from a loss of IR signal towards the edges and corners of the image due to fall off (e.g., reduced radiation intensity) of the illuminator, lens shading, image sensor aperture limitations (where the aperture at the camera sensor is not wide enough to capture sufficient light near the edges of the aperture), and angular effects of the IR band pass filter at the sensor (or camera) that permit too much ambient light into the camera. At the same time, the center of the image may be too bright (too much light intensity or radiation) due to too much concentration of light at the center of the image, and so much so that the center of the image may be washed out by the light intensity.

Attempts to compensate for these difficulties are performed by using digital gain (or in other words, lens shading correction for example) when the IR image is analyzed, displayed, and/or used to provide data to improve an RGB or RGBD (depth) image for example. However, for those applications that typically and automatically analyze signal-to-noise ratio (SNR) on an image, such as with face detection for example, the loss of IR signal also corresponds to a loss of SNR in the corners and edges of the image, causing some systems to fail to meet performance needs of the application. Thus, while the digital gain adjustments may adjust for the extreme high and low light intensity areas on the image providing adequate light intensity values for those areas, the digital gain adjustments cannot compensate for the loss of SNR.

Also, ambient light often degrades performance on the conventional IR or NIR illuminator systems. The conventional illuminator systems have sensors at cameras that receive the light emitted from the illuminator and reflected off of the object being detected. The sensors block ambient light by using an optical band pass filter. This may be a physical filter placed in front of the sensor. The conventional filter, however, also is configured to accommodate the emission characteristics for the LED illuminator and the angle of incidence characteristics of the filter. In some configurations, this may require that the passband of the band pass filter be more than 100 nm wide in order to better ensure sufficient inclusion of the desired relatively wide incident light angle of the incoming LED light reflected from the object being detected. The size of the incoming incident light angle depends on the field of view of the camera and optical characteristics of the lens. This undesirably allows significant ambient light into the NIR sensor or camera, resulting in a degradation in performance.

DESCRIPTION OF THE FIGURES

The material described herein is illustrated by way of example and not by way of limitation in the accompanying figures. For simplicity and clarity of illustration, elements illustrated in the figures are not necessarily drawn to scale. For example, the dimensions of some elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference labels have been repeated among the figures to indicate corresponding or analogous elements. In the figures:

FIG. 1 is an illustration of a user using an electronic device with a light projection and image capturing system being used for object detection and access authorization;

FIG. 2 is perspective close-up view of a conventional LED used for light projection;

FIG. 3 is a schematic diagram of a conventional LED IR light projection and image capture and processing system;

FIG. 3A is a far-field radiation emission distribution graph for conventional LEDs used in the system of FIG. 3;

FIG. 3B is a lens luminance intensity level graph for the system of FIG. 3;

FIG. 3C is a graph showing the captured energy as a function of wavelength for the system of FIG. 3;

FIG. 3D is a graph showing the numerical aperture for the image sensor in the system of FIG. 3;

FIG. 4 is a far-field radiation emission distribution graph showing conventional and proposed radiation distribution patterns according to at least one of the implementations herein;

FIG. 5 is a simplified top view of an example multi-VCSEL array illuminator according to at least one of the implementations herein;

FIG. 5A is a top view of a single VCSEL array used on the illuminator of FIG. 5;

FIG. 5B is a pair of graphs showing light intensity transverse modes that can be achieved depending on single VCSEL diameter according to at least one of the implementations herein;

FIG. 5C is a plan view of another example VCSEL array for at least one of the implementations herein;

FIG. 6 is a schematic diagram to explain diffused and specular light reflection;

FIG. 7A is a resulting IR image from an IR camera system showing significant performance degradation from speckle;

FIG. 7B is a resulting IR image from an IR camera system showing example reduced speckle degradation;

FIG. 8 is a resulting IR image from an IR camera system showing significant performance degradation due to speckle;

FIG. 9 is a resulting IR image from an IR camera system showing significant performance degradation due to speckle on an image of a face;

FIG. 10 is a cross-sectional side view of a vertical cavity semiconductor emitting laser (VCSEL) with a diffuser;

FIG. 11 is a cross-sectional side view of a vertical cavity semiconductor emitting laser (VCSEL) with a metalayer in accordance with at least one of the implementations herein;

FIG. 12 is a far-field radiation emission distribution graph showing a batwing pattern in accordance with at least one of the implementations herein;

FIG. 13A is a flow chart of a method of emitting light in accordance with at least one of the implementations herein;

FIG. 13B is a flow chart of a method of forming a light emitting device in accordance with at least one of the implementations herein;

FIG. 14 is a perspective close-up view of an example metalayer in accordance with at least one of the implementations herein;

FIG. 15A is a simplified top view of an example metalayer in accordance with at least one of the implementations herein;

FIG. 15B is a simplified side view of the example metalayer of FIG. 15A in accordance with at least one of the implementations herein;

FIG. 16 is a schematic diagram to explain the angular reflection and refraction using the metalayer in accordance with at least one of the implementations herein;

FIG. 17 is a simplified top view of another example metalayer in accordance with at least one of the implementations herein;

FIG. 17A is a perspective view of a post on a metalayer of FIG. 17 in accordance with at least one of the implementations herein;

FIG. 17B is a simplified top view of a post from the metalayer of FIG. 17 in accordance with at least one of the implementations herein;

FIG. 18 is a simplified top view of another example metalayer in accordance with at least one of the implementations herein;

FIG. 19 is a graph of the gain of a wavelength bandpass filter receiving LED light and ambient light;

FIG. 20 is a graph of the gain of a wavelength bandpass filter receiving VCSEL light and ambient light in accordance with at least one of the implementations herein;

FIG. 21 is a graph of the gain of a wavelength bandpass filter receiving light from an LED and showing RGB-IR cross talk;

FIG. 22 is a graph of the gain of a wavelength bandpass filter receiving light from a VCSEL and showing reduced RGB-IR cross talk in accordance with at least one of the implementations herein;

FIG. 23 is an illustrative diagram of an example light emitting and image processing system;

FIG. 24 is an illustrative diagram of an example system; and

FIG. 25 is an illustrative diagram of an example system, all arranged in accordance with at least some implementations of the present disclosure.

DETAILED DESCRIPTION

One or more implementations are now described with reference to the enclosed figures. While specific configurations and arrangements are discussed, it should be understood that this is done for illustrative purposes only. Persons skilled in the relevant art will recognize that other configurations and arrangements may be employed without departing from the spirit and scope of the description. It will be apparent to those skilled in the relevant art that techniques and/or arrangements described herein may also be employed in a variety of other systems and applications other than what is described herein.

While the following description sets forth various implementations that may be manifested in architectures such as system-on-a-chip (SoC) architectures for example, implementation of the techniques and/or arrangements described herein, other than the specific structure of an illuminator and sensor described below, are not restricted to particular architectures and/or computing systems and may be implemented by any architecture and/or computing system for similar purposes. For instance, various architectures employing, for example, multiple integrated circuit (IC) chips and/or packages, and/or various computing devices and/or consumer electronic (CE) devices such as set top boxes, smartphones, cameras, laptop computers, tablets, and so forth, as well as dedicated access authorization devices either for access to an electronic device or otherwise mounted or placed at a variety of physical locations may implement the techniques and/or arrangements described herein. Further, while the following description may set forth numerous specific details such as logic implementations, types and interrelationships of system components, logic partitioning/integration choices, and so forth, claimed subject matter may be practiced without such specific details. In other instances, some material such as, for example, control structures and full software instruction sequences, may not be shown in detail in order not to obscure the material disclosed herein.

The material disclosed herein, other than the specific structure of the IR illuminator and sensor described below, may be implemented in hardware, firmware, software, or any combination thereof. The material disclosed herein also may be implemented as instructions stored on a machine-readable medium, which may be read and executed by one or more processors. A machine-readable medium may include any medium and/or mechanism for storing or transmitting information in a form readable by a machine (for example, a computing device). For example, a machine-readable medium may include read-only memory (ROM); random access memory (RAM); magnetic disk storage media; optical storage media; flash memory devices; electrical, optical, acoustical or other forms of propagated signals (e.g., carrier waves, infrared signals, digital signals, and so forth), and others. In another form, a non-transitory article, such as a non-transitory computer readable medium, may be used with any of the examples mentioned above or other examples except that it does not include a transitory signal per se. It does include those elements other than a signal per se that may hold data temporarily in a “transitory” fashion such as RAM and so forth.

References in the specification to “one implementation”, “an implementation”, “an example implementation”, and so forth, indicate that the implementation described may include a particular feature, structure, or characteristic, but every implementation may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same implementation. Further, when a particular feature, structure, or characteristic is described in connection with an implementation, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other implementations whether or not explicitly described herein.

An illuminator with a metalayer for steering light.

As mentioned, an infra-red (IR) illuminator may be used for biometric detection or other applications. For example, such biometric detection may be related to face recognition or iris illuminators and IR imaging systems including face login and other near infrared (NIR) centric techniques, usages, devices, and the like. Such techniques, usages, devices, and the like may require controlled NIR illumination to generate an image with the specific characteristics needed for face recognition or other usages.

Referring to FIG. 1, an example face login system 100 is shown where a user 102 faces an access authorization device 104, which in this example may be a computer or laptop with an IR illuminator (or projector) 106, and a camera or sensor 108 that detects light projected from the IR illuminator and reflected from an object 102 to be detected such as the user's face. Such an arrangement conventionally is performed by using an LED illuminator emitting NIR light.

Referring to FIG. 2, an example LED die 200 may emit light in a Lambertian pattern in such an illuminator. Due to the large change in index of refraction between the semiconductor material (e.g., close to 4) and air (e.g., 1) most of the energy is reflected back into the substrate leading to low extraction efficiency. A lens may be provided over the LED die to narrow the beam and/or to make a side-emission pattern. For example, the lens for a surface mounted LED may be pre-formed molded plastic (e.g. silicone), which is bonded to a package in which the LED die is mounted. Bonding the lens to the semiconductor may couple the light energy into the lens which uses the curved surface to both improve extraction efficiency and to control the beam angle. A face login device may use an LED with a refractive element to focus the light onto the target, such as the example illuminator 200.

Referring to FIG. 3, an example conventional LED IR projection system 300 has an LED illuminator 302 that is emitting light onto an object 304, which may be a face for detection, but a test screen is shown here to exemplify experiments to improve the conventional system. The LED may be emitting light in a far-field radiation pattern shown on graph 314 (FIG. 3A). A camera may receive the reflected light and may have imaging optics that receive the light emitted from the LED illuminator 302 and reflected from the object 304, and may include a lens 306 and an optical filter 308. The lens 306 may provide a light reception pattern as shown on luminance intensity level graph 316 (FIG. 3B), while the optical filter 308 may limit the spectral response of the camera as exemplified by the wavelength graph 318 (FIG. 3C). A sensor 310, which may be for monochromatic light such as IR or may be for a combined RGB-IR light sensing, may receive the light, as limited by the sensors numerical aperture as represented by an optical efficiency graph 320 (FIG. 3D) and produce raw image data as illustrated on image 312.

Also as mentioned above, and as shown on LED IR radiation distribution graph 314, the conventional LED IR illuminators for many different applications including object detection and face detection, provide IR images with low SNR at the edges and corners of the image. This may be due to fall off (radiation reduction) of the illuminator, lens shading, image sensor aperture, angular effects of the IR band pass filter (the band pass filter being too narrow for the emission angle of the LED and resulting incoming light incidence angle to the BPF), or the like. This fall off can be seen by the various results at the edges and corners of the graphs FIGS. 3A-3B.

In such examples, the target distance and screen characteristics may be set by the application requirements, and the system may be configured to offer a minimum SNR across the field of view of the camera. However, each of the elements (or LEDs) may have a tendency to be less efficient at increased angles such that the non-uniform characteristics may aggregate. For example, it may be possible to compensate for the fall off only in the illuminator such as by using diffractive elements as discussed below, which may increase the size and cost of the illuminator.

Referring to FIG. 4 for more detail, as one specific example, such an approach that uses an LED covered by a lens limits the ability to control the emission pattern in order to provide uniform light intensity in combination with high extraction efficiency (e.g., here referring to minimizing the emission light outside of the image input angle needed to form an entire image). For example, the optics may be designed to narrow the emission angle to increase efficiency, but the radiation intensity will fall off proportional to the sine of the emission angle increasing as the emission angle increases. Far-field radiation pattern graph 400 shows the conventional radiation curve 402 (on one side of the camera viewing angle from 0 to about 60 degrees). This is similar to radiation distribution graph 314 (FIG. 3A). At 0 degrees, the relative intensity is at 1.0 which is too high and may cause washout as mentioned above. At the edge of a camera viewing angle (or referred to herein as the outer image emission angle, which may be less than the total emission angle) and that would form the edges of a resulting image, here about 20-25 degrees but would depend on the configuration of the LED package, the intensity has already fallen too low (fallen 20%) so that the intensity from 0 to the outer edge of the viewing emission angle at 20-25 degrees is not very uniform. Also, the fall-off at greater emission angles than the outer image emission angle is relatively mild (non-steep) so that there is still 20% intensity at 60 degrees and does not reach 0 intensity until 100 degrees at the outer limit of the total emission angle, which is significant wasted energy and power that could be used elsewhere on the camera (or imaging device), or could permit such a device to have a longer battery life.

Such losses conventionally are compensated for by using digital gains (e.g., lens shading correction), but the loss of signal corresponding to a loss of signal to noise ratio (SNR) in the corners causes some systems to fail to meet performance needs of various applications. The low SNR has been found to result from the lack of light intensity from the LED at the outer or edge image emission angle (herein this example at about 20-25 degrees).

Therefore, a better balance is needed between uniformity (e.g., obtained by providing a wide emission angle so sufficient light intensity reaches the whole image) and efficiency (by narrowing the emission angle). Specifically, a desired radiation distribution curve 404 is shown on graph 400. In order to reduce the center washout effect, the illuminator center (at 0 degrees) should have lower intensity (here lowered by about 20%). It has been found that the intensity at the outer image emission angle at part 408 of curve 404 (20-25 degree region for example) should not just remain flat, but should be increased by about 20% greater than the normal emissions in order to compensate for the undesired effects mentioned above and provide adequate SNR and intensity at the edges and corners of an image. Greater than the outer emission image angle (part 410 of curve 404), it is desirable to make the radiation distribution curve fall-off as sharp (or steep) as possible to reduce wasted energy and power. Here, it was found to be desirable to drop to 0 intensity by about 60 degrees. The ways to achieve these parameters are described below.

Another parameter that was found to affect the quality of the resulting image is ambient light. Ambient light may degrade performance when too much of the ambient light is able to reach the sensor. The acceptance of ambient light may be reduced through the use of an optical band pass filter; however, to accommodate the emission characteristics for the light emitting diode (LED) illuminator and the angle of incidence characteristics of the filter, the passband of the bandpass filter often must be more than 100 nm wide or more, which may allow too much ambient light into the camera, which affects the light intensity pixel values of the resulting image. Such problems may apply particularly to face and iris scanning as mentioned above, eye tracking, and any NIR camera that relies on active illumination and is expected to work in ambient light conditions.

To resolve these issues and achieve the desired radiation distribution pattern (or emission pattern), a vertical-cavity surface emitting laser (VCSEL) illumination source may be used instead of the LED, and which may offer a smaller and more controlled source of illumination with greater collimation as well as narrower emission wavelengths. The VCSEL may provide a reduced emission angle that better matches the camera viewing angle to reduce waste at the outer limits of the angle that is outside the outer (or edge) image emission angle. The use of the VCSEL also provides a more desirable illumination over a narrower wavelength band so that the band pass filter can have a reduced passband, thereby blocking more ambient light from entering the camera to provide a better quality image.

The use of the VCSEL, however, does not provide the desired intensity peaks at the outer image emission angle (the 20-25 degree region as one example on graph 400) and results in undesirable, severe, high-contrast speckle. Specifically, laser (VCSEL) light is inherently narrow band; however, when a light source (such as the VCSEL) is coherent such that it emits light at substantially a single wavelength at a single phase for example. When this light reflects off a rough surface, multiple paths of various lengths are generated between the illuminator and detector and the light from various paths may interfere with each other in the detector, combining in constructive or destructive manners. This combining works to form patches of higher intensity light and lower intensity light due to the resulting constructive interference where light waves combine, and deconstructive interference where light waves subtract from each other. In an image detector with a finite aperture such as on camera sensors, and which are much like the human eye, these varied patches of intensity appear as optical “speckles,” as some small portions spots, or blotches of the image look brighter than other small portions. Further, this spot-to-spot intensity difference can vary depending on an observer's (or sensor's) position, which makes the speckles appear to change when the observer or sensor moves.

Referring to FIG. 6, a light reflection diagram 600 shows the difference between diffused and specular light that forms speckles. The speckle can be computed as the coherence of the diffuse light, and the speckle may be determined by:

I _(D) =L·NCI _(L),  (1)

L·N=|N|L|cos α=cos α  (2)

where I_(D) is the intensity of diffusely reflected light, L is the light direction vector from a surface to the light source, N is the surface's normal vector, and N and L are normalized, C is color, I_(L) is the intensity of incoming light, and α is the angle between the two vectors. Thus, the speckle is formed when some wavefronts add and others subtract causing small uneven light and dark spots or blotches on the sensor which vary based on the distance to the object.

Referring to FIGS. 7A-7B and 8-9, one example of severe high-contrast speckle is provided on speckled image 700 and corrected in image 702 where both images show the same mannequin 704. The areas with reduced speckle can be seen where the image has a flatter, more uniform color and brightness without (or reduced) dots, blotches, and so forth. Images 800 (plain surface) and 900 (a face) provide other examples with severe non-uniformities introduced by speckle that may render the image unsuitable for various applications. By one example, the speckles may interfere with object detection analysis of objects in the images.

Referring to FIG. 10, one attempt to reduce speckles (and increase overall uniformity) is accomplished by spacing an optical diffuser further away from the VCSEL as shown on lighting device (or lighting package) 1000. Lighting device package 1000 shows a VCSEL 1002 in a body or casing 1004. The VCSEL 1002 here is placed on an electrical contact 1006 and has a substrate 1008, distributed Bragg reflector (DBR) (or mirror) layers 1010 and 1012, an active region 1014 of quantum well and barrier layers between two confinement layers 1016 and 1018. A metal contact 1020 surrounds a plastic silicone lens 1022 that emits light 1024. A diffuser 1026 may be placed above, and spaced from, the VCSEL 1002 in order to diffuse and emit the light in a less coherent pattern 1028. This configuration of device package 1000, however, introduces a performance/size tradeoff forcing the package to be taller to hold the diffuser 1026, which may be undesirable in many small form factors and may increase cost.

Instead, speckle of such VCSEL illuminators may be eliminated or reduced by using an illuminator to emit an illumination beam where the light source comprises a set (or array) of vertical-cavity surface emitting lasers (VCSELs) that may be arranged on a single substrate. The emission wavelengths from different elements of the array may have different values that are separated by about 1 nm or less, by one example, or may even include multiple VCSEL arrays each with a different mean wavelength, and again by one form, that is different by 1 nm or less. Thus, by varying laser emission wavelengths of the VCSEL elements in the VCSEL array, the array produces a resulting image with multiple overlapping speckle patterns which average to result in low-contrast speckle (referred to herein as reduced speckle). The VCSEL array may accomplish this without creating significant limitations on the imaging capabilities of the host illumination system. Each VCSEL array on the illuminator may be arranged in one-dimensional (or single row) configuration or a two-dimensional configuration as shown on VCSEL array 500 (FIG. 5) and described in detail below (FIGS. 5A-5C).

The VCSEL also does not substantially contribute to the shaping of the intensity peaks on the radiation distribution. Thus, as to the shaping of the radiation distribution pattern to provide a more uniform light intensity, a metalayer (also interchangeably referred to herein as a metamaterial, metasurface, meta-lens, metamaterial lens layer, metamaterial layer, beam shaper, or any combination of these). The metalayer is structured to make SNR more uniform, and in a relatively small package such as less than 1.5 mm in the Z (height)−dimension by one example.

Referring to FIG. 11, a light package or device (or illuminator) 1100 has a similar VCSEL structure as device 1000, and the layers are numbered similarly, except here body 1104 may be flat or shorter since no diffuser is provided above the VCSEL to hold the diffuser as with casing 1004 so that here the package 1100 can be shorter. Also, the metalayer 1122 may replace the plastic lens 1022 of package 1000 to redirect and emit the light received from the VCSEL 1102. When an array of VCSELs are provided on an illuminator, each VCSEL may have its own metalayer 1122 as shown on the single VCSEL on illuminator 1100. The VCSEL provides a fall-off at the outer wings of the radiation distribution pattern, outside of the outer edge incident angle (or image emission angle), reaches 0 light intensity at about 60 degrees by one example approach, and by another form, at about 45 degrees or less, and by one form, at 45 degrees. The metalayer, however, forms the peaks and valley in the light intensity radiation to form or shape the upper end of the radiation distribution pattern to form a batwing shape as described in greater detail below.

By another form, an illuminator comprising at least one light source has a stack of layers comprising a layer with a light emitting surface. While the light source could be an LED, by another approach the light source is a monochromatic light source, and in one form, is an infra-red (IR) or near-infra-red (NIR) illuminator that comprises a vertical-cavity surface emitting laser (VCSEL). The light emitting surface may be the DBR layer 1112 by one example. Also, a metalayer is disposed at the stack of layers to receive light from the light emitting surface. The metalayer may have a plurality of spaced light scattering posts (also referred to by many names including optical antennas, meta-atoms, nanostructures, nanoparticles, nanoscatterers, subwavelength scatterers, and resonators) to receive light from the light emitting surface and steers the output light to form the desired radiation pattern. Post here simply refers to the post extending away from a substrate surface to form a distinct structure from the substrate and does not necessarily mean the height of the post is greater than a width or diameter of the post, nor that the post must extend vertically relative to the earth.

Referring to FIG. 12, furthermore, the illumination pattern also may be controlled by using the metalayer placed on the emitting surface of the light source, or VCSEL, to generate the desired light intensity peaks at the outer image emission angles (the angles that will form the outer edges and corners of the image) which is a smaller angle than the total emission angle. This is performed while reducing the light intensity at the center (or optical axis) of the illuminator, and in turn, the resulting images. This is achieved by establishing a far-field batwing (or M-shaped) light intensity or radiation distribution pattern 1202 (referred to herein as the batwing pattern (FIG. 12)), and the metalayer may be arranged to form the desired illumination pattern for a specific application such as the batwing pattern.

By using a VCSEL with a metalayer as the illuminator, the illumination pattern of the VCSEL may be controlled or tuned for the application resulting in the outer wings 1208 of the batwing pattern 1202. The batwing pattern 1202 may be defined by having two roughly equal peaks 1210 with a valley 1204 between the peaks 1210 at about 0 degrees in emission angle. By one form, the batwing shape is characterized by a U-shaped valley 1204 or a valley with a pointed bottom, where, by one example, there is no substantially flat, horizontal, constant light intensity radiation within the valley. By one form, the bottom of the valley 1204, near 0 degrees in emission angle by one example, reaches about 80% light intensity, or about 20% less light intensity than the peaks 1210. By another example, the valley reaches about 30-40% less intensity than the peaks, and by one form, about 35% less light intensity than the peaks.

This is accomplished by arranging the posts on the metalayer to generate the desired batwing radiation pattern 1202 or other pattern. Thus, the light source and metalayer are arranged to cooperatively form a far-field batwing radiation pattern of light emission comprising a lower light intensity valley part between two peaks of light intensity parts along the batwing radiation pattern. By one form, the peaks have the greatest amount of light intensity on the entire batwing pattern. This results in greater SNR at the edges and corners of the image, and more uniform SNR over the whole image. The details are provided below

It also will be noted that the batwing distribution pattern 1202 also may have a fall-off portion 1206 and flaring end portion 1208 until light intensity is zero. This fall off portion is outside of the outer image emission angle (herein 20-25 degrees in this example) but still within the total emission angle which may be out to about 100 degrees in this example. The VCSEL may have better emission control with a narrower total light emission than a comparable LED and cause these sections to fall steeper and reach 0 light intensity at a smaller total emission angle than the LED. This results in the reduction of wasted energy. The use of a VCSEL(s) instead of the LED also reduces ambient light interference at the sensor (or camera) also explained in greater detail below.

By one approach, the light source and metalayer are arranged to cooperatively form a predetermined far-field light intensity radiation pattern. By one form, to accomplish this, the far-field radiation pattern may be shaped to increase a uniformity of light intensity on a resulting image formed from reflecting the emitted light on an object. Particularly, the predetermined far-field light intensity radiation pattern may be shaped to compensate for non-uniformities in the light intensity caused by the VCSEL, and particularly by forming the batwing shape as described herein.

Referring to FIG. 13A, an example process 1300 for emitting light to capture images described herein is arranged in accordance with at least some implementations of the present disclosure. In the illustrated implementation, process 1300 may include one or more operations, functions or actions as illustrated by one or more of operations 1302 to 1306 numbered evenly. By way of non-limiting example, process 1300 will be described herein with reference to any of the example light emitting or image processing systems or devices described herein and where relevant.

Process 1300 may include “emit IR or NIR light from at least one vertical-cavity surface emitting laser (VCSEL)” 1302, and as described above, this better controls the emission than an LED to reduce power consumption and with a narrower wavelength emission enables reduction of the harmful effects of ambient light at the band pass filter of the sensor (or camera) by reduction of the width of the passband of the filter. This may occur at a light source that uses a single VCSEL, a single array of VCSELs, or multiple VCSEL arrays. When an array of VCSELs has individual or each VCSEL emitting at a different wavelength, the number of wavelengths in the array average the speckle thereby reducing the contrast of the speckle. This can be applied to multiple VCSEL arrays as well where each VCSEL array has a dominant average wavelength that is different form the dominant wavelength of the other arrays. By one form, the wavelength difference between individual or each VCSEL in an array is at least about lnm, or the difference between dominant or average wavelengths of multiple VCSEL arrays is at least about 1 nm or less. The details are explained below.

Process 1300 also may include “redirect the light from the VCSEL by a metalayer disposed on the VCSEL” 1304, and particularly, the device may have circuitry and contacts to apply an electric current across the VCSEL and metalayer to induce the light from the VCSEL into a desired generally vertical direction of propagation into and through the metalayer with light oscillations that impact the metasurface posts, changing the phase of the light that transmits through the posts. The details are explained below.

Process 1300 may continue with the operation “emit, by the metalayer, the light in a far-field batwing radiation pattern having shape at least partially formed depending on the structure of the posts on the metalayer” 1306. Thus, the arrangement of posts on the metalayer significantly contributes to an emission radiation pattern to provide a more uniform light intensity across the total emission angle of the light source. By one approach, light scattering posts on the metalayer are sized, shaped, and spaced from each other in both distance and direction to generate the batwing pattern. This results in increased SNR at the edges and corners of an image, while reducing (or at least maintaining) the light intensity at the center of the image. The details are explained below.

Referring to FIG. 13B, an example process 1350 for forming a light emitting device described herein is arranged in accordance with at least some implementations of the present disclosure. In the illustrated implementation, process 1350 may include one or more operations, functions or actions as illustrated by one or more of operations 1352 to 1356 numbered evenly. By way of non-limiting example, process 1350 will be described herein with reference to any of the example light emitting or image processing systems or devices described herein and where relevant.

Process 1350 may include “form an infra-red (IR) or near-infra-red (NIR) illuminator comprising at least one vertical-cavity surface emitting laser (VCSEL) having a layer with a light emitting surface” 1352. The light emitting surface may be a top layer of the VCSEL itself and may be a DBR layer. This also may include forming one or more arrays of VCSELs on the illuminator to reduce speckle as mentioned above and explained in detail below.

Process 1350 also may include “form a metalayer having a plurality of spaced light scattering posts disposed to receive light from the light emitting surface and redirect the light” 1354. By one example, this also includes forming a metalayer on each or individual VCSELs on one or more arrays of VCSELs.

Process 1350 may continue with the operation “arrange the VCSEL and metalayer to cooperatively form a far-field batwing radiation pattern of light emission comprising a lower light intensity valley part between two peaks of light intensity parts along the batwing radiation pattern” 1356. Thus, it is the metalayer that significantly contributes to the radiation pattern by arranging the scattering posts as mentioned above. This results in much more uniformity in light intensity across the image emission angle (and in turn, the camera viewing angle) thereby increasing the light intensity, and in turn the SNR, at the edges and corners of an image, while reducing the light intensity at the center of the image.

By one approach, this operation also comprises forming the metalayer with a base portion, and the posts extending from the base portion. The base portion is disposed adjacent the VCSEL to receive the light emitted from the VICSEL. The posts are sized, shaped, and spaced in both direction and distance to impart a phase on the wavefront as a function of position on the VCSEL surface, thus producing the desired far-field radiation pattern.

Referring to FIGS. 14-18, the metalayer is described in more detail. Referring specifically to FIG. 14, an example metalayer (or metasurface) 1400 may have an array 1402 of the posts 1404 on a base or substrate 1406 that is flat or otherwise generally planar with a thickness of th_(b) of about one-half the dominant wavelength. The base 1406 may be placed on an upper surface 1410 of a top or upper layer 1408 of a light source 1412 such as an LED or here a VCSEL. The top layer 1408 of the light source may be a DBR for example. The size of each post 1404 including the height H and width W (or diameter D when the shape of the post is circular or curvalinear as explained below) as well as the spacing ‘a’ between posts and arrangement of the posts relative to each other all may be selected to steer the light to form the desired far-field light intensity radiation pattern, such as the batwing pattern 1202 (FIG. 12). By one form W (or D) is about four to ten times smaller than the wavelength of the light received from the light source and H is at most two times smaller than the wavelength of the light. The details are explained below.

To understand the metalayer, the physics of the motion of the light must be understood. When a plane electromagnetic wave encounters a boundary between two homogeneous media with different refractive indices, it is split into a reflected beam that propagates back into the first medium and a transmitted (or refracted) beam that proceeds into the second medium. The reflection and transmission coefficients and their directions may be determined by the continuity of electric field components at the boundary between the two media and may be given by the Fresnel equations and Snell's law, respectively.

Referring to FIG. 15A, a metalayer 1500 has an array 1502 of posts 1504 on a substrate 1506. Light is propagated from a light source, such as the LED or VCSEL, forming a light wave L shown in dashed line, where it oscillates left and right while it flows in the propagation direction P, and has a wavelength λ. The wave is forced to propagate in the desired direction P by running an electric current in a transverse direction E to the desired direction P of propagation. For dielectric nanodisk layers, incident radiation or light brings both electric and magnetic responses of comparable strengths. The coupling of incoming light to the electric field's circular displacement current E results in a strong magnetic dipole resonance in direction M. The magnetic resonance and light coupling occurs when the wavelength of the light traveling through the posts is a multiple of the lateral dimension of the posts—that is, when the size of the post is:

post diameter D≈λ/n,  (3)

where n is the refractive index of the post material, and λ, is the light's wavelength.

If an array of the posts 1504, which act as subwavelength resonators, have negligible thickness and are added to a light emitting interface or surface 1508, the reflection and transmission coefficients may be changed because the boundary conditions are modified by the resonant excitation of the effective current within the surface. For example, the reflection and transmission waves may carry a phase change that may vary from −π to π, depending on the wavelength of the incident wave relative to the surface electric/magnetic resonance and other parameters of the metalayer as explained below. When the phase change is uniform along the interface (without posts), the directions of reflection and refraction may be unaltered. In contrast, metalayer posts create spatial phase variation caused by having the posts separated by another media such as the air between the posts for example with subwavelength resolution (or post widths) to effectively control the direction of wave propagation and the shape of the resulting wavefront. Such control may be useful for beam focusing/steering applications or the like as mentioned herein.

Thus, a metalayer may bend light, and any periodic two-dimensional structure the thickness and periodicity of which are small compared to a light wavelength in the surrounding media may be characterized as a metalayer. For example, metalayers may provide degrees of freedom in designing spatial inhomogeneity of optical response over an optically thin interface. In some implementations, metalayers also may offer the advantage of taking up reduced physical space since the metalayers may be extremely thin, measured by nanometers as here.

The metalayers manipulate the wavefront (phase and amplitude), polarization, and intensity of light, and operate at most efficiency when receiving light at one uniform wavelength, as with other diffractive optical devices. Such dielectric transmit-arrays are very versatile metalayers because they provide high transmission and subwavelength spatial control of both polarization and phase.

The metalayers produce abrupt and controllable changes of optical properties by engineering the interaction between light and the array of posts. Therefore, metalayers may introduce a spatially varying electromagnetic or optical response (e.g., scattering amplitude, phase, and/or polarization). In other words, by tailoring the properties of each element of the post array, the phase of the scattered light may be spatially controlled and consequently “mold” the wavefront.

Referring to FIG. 16, the transmission or reflection angles can be computed as a function of incident angle and phase gradient of a metalayer with the following equations.

$\begin{matrix} {{{{Transmission}\mspace{14mu} {Mode}\mspace{14mu} n_{t}\sin \; \theta_{t}} - {n_{i}\sin \; \theta_{i}}} = {\frac{\lambda}{2\pi}\frac{d\; {\phi (x)}}{dx}}} & (4) \\ {{{{Reflection}\mspace{14mu} {Mode}\mspace{14mu} \sin \; \theta_{r}} - {\sin \; \theta_{i}}} = {\frac{\lambda}{2\pi \; n_{i}}\frac{d\; {\phi (x)}}{dx}}} & (5) \end{matrix}$

where x is a coordinate in the plane separating incident beam and transmitted beam, θ_(t) is the transmission angle, θ_(i) is the incident angle, θ_(r) is the reflective angle,

$\frac{\partial\Phi}{\partial x}$

is the gradient of the phase along the plane of the metalayer, and λ is the wavelength of light. The metalayer is arranged such that the gradient achieves the desired transmission angle (view). The gradient of the phase is tuned by the distribution of post's diameters on the surface.

As mentioned, each of the dimensional parameters of the posts, including the size, shape, and spacing of the posts in both distance ‘a’ and direction, may contribute to the coherence of the light and the radiation distribution pattern, and in turn the SNR. The size was already mentioned above where the selected post diameter D should at least be smaller than the light wavelength, and the post diameter D should be set so that the wavelength is a multiple of the post diameter D. The phase of the transmitted light, which is the sum of the incident and forward scattered light, can be controlled to take any value in the 0 to 2π range by properly selecting the post diameters. The local transmission coefficient of an array of posts with gradually varying diameters can be approximated by the transmission coefficient of a uniform periodic array of posts. The subwavelength lattice constant and the large number of phase steps provided by the continuous post diameter-phase relation, enables accurate implementation of exotic phase profiles that may be customized for specific applications as described above. By one form, post diameter D should be set at about λ/10 to λ/4 to provide a desired phase from 0 to 2π.

As to the shape of the posts, the posts with various geometries and arrangements impart different phases to the transmitted light, shaping its wavefront to the desired form. For posts 1404 such as rectangular dielectric cuboid as one example (FIG. 14), a form of birefringence is induced, and the metasurface optical response is highly sensitive to the polarization of the incident radiation. However, each of the posts could be considered as a short waveguide when provided with a circular cross section (and therefore curved lateral sides) truncated on both top and bottom, and operating as a low-quality-factor Fabry-Perot resonator. The circular cross section of the posts leads to the polarization insensitivity of the lens. Because of the high refractive index contrast between the posts and their surroundings, the posts behave as independent scatterers with small cross coupling. The phase and amplitude of the scattered light strongly depend on the diameter of the posts.

Thus, instead of rectangular shapes, curved shapes may be used. Specifically, centrosymmetric subwavelength features may be used with curvalinear sides in top view such as cylinders which enables the metalayer to operate with non-polarized light. This example is provided by posts 1504 on metalayer 1500 (FIG. 15). Top view here refers to facing the flat surface 1508 of the metalayer 1500.

As to the spacing of the posts, a top view of a portion of a metalayer 1500 is shown with the array 1502 of the posts 1504, here being (cylindrical posts) of a dielectric material. The posts are arranged in top view of the metasurface in a hexagonal lattice, by example with a lattice constant of approximately λ/2. Metalayer 1700 (FIG. 17) also has a similar hexagonal lattice spacing. Note that other lattice types could also be chosen.

Referring to FIGS. 17 to 17B, an example of a beam steering metasurface design that is polarization insensitive and has posts in an elliptical shape. Metalayer 1700 is an example metasurface with varying post diameters that result in “phase gradient” to steer an incident beam towards a given direction. Specifically metalayer 1700 has an array 1702 of posts 1704 on a substrate 1706. The posts are elliptical and have a major axis D_(x) and a minor axis D_(y) where the major axis is parallel to an angle θ from horizontal (or horizontal edge of the substrate 1706 in top view). Both the axes lengths D_(x) and D_(y) as well as the angle θ may be varied depending on the position of the post on the substrate 1706 of the metalayer 1700.

FIG. 18 illustrates another example metalayer 1800 composed of an array 1802 of posts 1804 on a flat base (substrate) 1806. The posts have height and outer width dimensions of about 100 nm or less, which is a subwavelength. Here, the posts are non-symmetrical, non-regular shapes such as L-shaped or various rotated V-shapes in top view and with a sequence that is repeated across each row on the metalayer 1800. These shapes in this sequence are used to improve the broadband response as a function of wavelength and incident angle. A metasurface is disclosed by N. Yu et al., Flat Optics with Designer Metasurface, nature materials, vol. 13, February 2014.

Thus, it will be understood that the posts may have many different arrangements of size, shape, and spacing on the metalayer in order to act as the diffuser to reduce the coherence of the light and to shape the emission far-field radiation pattern to the desired batwing pattern. By one form, in order to reduce cohesion and provide the far-field batwing radiation distribution, the spacing of the posts should be hexagonal lattice with a distance of half of the wavelength from post to post, and with cylindrical or elliptical posts with a diameter that varies from λ/10 to λ/4. The arrangement of the posts can be dimensioned as described below. The desired metalayer phase distribution for a given “output phase distribution” is extracted using the algorithms shown below. The phase depends on the size of the post, and by one example changing from 0 to 2πwhen the size of the post changes from 1/10 wavelength to ¼ of the wavelength.

As arranged, the metalayer can be understood to act as a beam shaper, and as mentioned, providing the metalayer with a certain structure can shape the phase distribution of a wave emitted from the metalayer and to form the batwing shape of the radiation distribution. Also, the desired phase distribution is generally realized by controlling the size distribution of the posts. Thus, the fabricated beam shaper works most effectively with light from a single uniform selected wavelength since the phase modulation depends on the light propagation inside the material. Therefore, the thickness of the developed metalayer (e.g., the height on the stack of layers) is approximately half of the wavelength and the resulted phase change is wavelength dependent.

The phase distribution of the metalayer may be generated at a desired wavelength to produce the desired far-field batwing radiation pattern. This may be accomplished by controlling monochromatic wave propagation and using the far-field assumption, all while the Fourier transform is used to model the wave propagation. Such operations are disclosed by G. Yang and B. Gu, On the amplitude-phase retrieval problem in the optical system, Acta Phys. Sin. 30, 410-413 (1981); B. Gu, G. Yang, and B. Dong, General theory for performing an optical transform, 15 Sep. 1986, Vol. 25, No. 18, Applied Optics; or S. R. W. Gerchberg and W. O. Saxton, A practical algorithm for the determination of phase from image and diffraction plane pictures, Optik 35, 227-246 (1972).

Alternatively, an iterative algorithm (based on rigorous coupled-wave analysis) for constructing a metalayer can be use as disclosed by Ni Y. Chang and Chung J. Kuo, Algorithm based on rigorous coupled-wave analysis for diffractive optical element design, Journal of the Optical Society of America A Vol. 18, Issue 10, pp. 2491-2501 (2001); https://doi.org/10.1364/JOSAA.18.002491. Since rigorous coupled-wave analysis (instead of Fourier transformation) is used to calculate the light-field distribution behind the metalayer, the metalayer can thus be better designed.

Fabrication of the Metalayer

Planar metamaterials with subwavelength thickness, or metalayers, with a single-layer or few-layer stacks of generally planar structures, may be fabricated as follows. To form the metalayer on the VCSEL (or LED or other stacked layer light source), a flat wafer of the desired material of the metalayer may be formed by chemical vapor deposition, doping, ion implantation, and/or etching. This provides a flat, planar surface to build the posts on. The posts are then formed on the flat surface of the wafer, and may be formed using nanofabrication methods of many different types of lithography such as optical, electron-beam, nanoimprint, multiphoton, x-ray, stencil, charged or neutral particle, and/or scanning probe lithography, as well as molecular self-assembly, laser printing, nanoprinting, and proton beam writing. The fabricated metalayer may be formed on the top layer of the light source, such as the DBR layer of the VCSEL, or may be formed separately and placed onto the light source thereafter.

Material of Metalayer

The initial metalayers were formed of arrays of metallic posts, whose Ohmic losses are significantly large and strongly affect the converting efficiency, especially in near-infrared and visible wavelength range. All-dielectric (or completely substantially dielectric) metalayers have been considered to avoid Ohmic losses. Owing to their low losses in the visible spectral range, all-dielectric metalayers allow for the realization of practically absorption-less functional devices for wavefront manipulation. In that case, in order to use desirable high refractive index dielectric materials as the metalayer, the diameter of the posts should be subwavelength in size (according to the condition D≈λ/n described above) to control the emitted phase and propagation directions.

To achieve these parameters by one example, the metalayer may be formed of TiO_(x) where is x is between about 1 and about 2, and by another form, 1<x<2. It has been found that the use of TiO_(x) at least with x<2 provides a transparent material that enables a larger refractive index and better scattering efficiency (minimizes optical loss) of the lighting device with the metalayer. The Titanium Oxide may be lightly doped with nitrogen or sulfur. By using Titanium Oxide, optical efficiencies may reach greater than about 90%.

By other examples, the metalayer may be formed of silicon, a-Si, or silicon-germanium with Germanium content less than about 20%. The addition of Ge in silicon also results in better scattering efficiency and better transmission efficiency for the metasurface compared to conventional silicon. Otherwise, the metalayer may be formed of SiO₂ or GaP.

Referring now to FIGS. 5 and 5A-5C, a meta illuminator may provide one or more VCSEL arrays to reduce the speckle. On conventional VCSEL arrays, each VCSEL in the array tends to have very close to the same wavelength, about or less than 1 nm difference. This is due to the close proximity of the emitter elements within the array and the uniform wafer characteristics of the usually epitaxially grown laser structure. Therefore, the individual VCSELs in a conventional 2D VCSEL array form speckle patterns that are nearly identical. These patterns combine to form high contrast speckle where the difference between the dark and light speckle spots can be greater than with a single VCSEL. High contrast speckle results in high levels of noise in the image that can wash out the actual image data (or signal) such that the speckle limits the ability of an imaging system to resolve fine spatial detail on an image. When mere low contrast speckle is present, either the speckle is sufficiently small so that image data (or signal) around the speckle is sufficient to reconstruct the image data (or is so small it is not needed), or the image data (or signal) can be discerned through the relatively dispersed, low-contrast speckle itself.

One solution to reduce the contrast of the speckle is to attempt to emit multi-wavelengths among the elements of the VCSEL array since sufficiently different wavelengths will not cleanly combine and subtract from each other but will average out instead resulting in lower contrast speckle. Specifically, when a surface, such as the object receiving light projected from the illuminator, is illuminated by a light wave, according to diffraction theory, each point on the illuminated surface acts as a source of secondary spherical waves and forms a scattered light field of reflected light traveling toward the camera sensor. The light at any point in the scattered light field is made up of waves which have been scattered from each point on the illuminated surface. If the surface is sufficiently rough to create path-length differences exceeding one wavelength, giving rise to phase changes greater than 2π, the amplitude, and hence the intensity, of the resultant light varies randomly. If light of low coherence (i.e., made up of many wavelengths) is used, a speckle pattern will not normally be observed because the speckle patterns produced by individual wavelengths have different dimensions and in this case, the average of the wavelengths is the dominant wavelength that is established and is impacted at the sensor. Thus, speckle contrast reduction is essentially the creation of many independent speckle patterns, so that the wavelengths average out on the retina, or in this case, the detector's sensor. This can be achieved by wavelength diversity, i.e., use of laser sources which differ in wavelength by a small amount, and on either a single VCSEL array or among multiple VCSEL arrays.

In more detail, speckle reduction is based on averaging S independent speckle configurations within the spatial and temporal resolution of the detector, and where each configuration has a different wavelength. It has been found that, under the most favorable conditions, where all the S independent speckle configurations have equal mean intensities, the contrast is reduced by a factor of √{square root over (S)}. For example, if an array of VCSELs has each VCSEL emitting a different dominant wavelength, then speckle will be reduced. The wavelength separation depends on the surface on which imaging is taken (e.g. facial skin).

A speckle pattern depends on the wavelength of the illuminating light. The speckle patterns from two beams with different wavelengths become uncorrelated if the average relative phase-shift created by the surface is ≥2π. Thus, the wavelength difference should be:

δλ≥λ²/2z  (6)

where z is the surface profile height variation of the illuminated surface. For example if wavelength if λ=0.85 μm and height variation z=0.1 mm, the wavelength difference should be ≥3.6 nm.

Referring to FIGS. 5 and 5A, the illuminator 500 may have a substrate 510 with one or more VCSEL arrays, and here four such arrays 502, 504, 506, and 508, each having an array of VCSELs 512, and where each VCSEL array 502, 504, 506, and 508 has a different dominant or average wavelength λ₁, λ₂, λ₃, or λ₄ respectively as shown. According to the present example, each dominant wavelength λ₁, λ₂, λ₃, or λ₄ is at about 1 nm or less different than any of the other dominant wavelengths. The aperture (or effective diameter) of the individual VCSELs may be about 2 μm or less.

Alternatively, an illuminator may have a single VCSEL array where each or a sufficient number of individual VCSELs on the array emit different wavelengths, again by one example, about 1 nm or less different. Other alternative examples could have the difference at about 1 nm or more difference.

Referring to FIG. 5B, single transverse mode laser diode arrays have been desirable for creating high power laser diode sources capable of achieving both high beam quality and spectral control. The transverse mode is the number of separate dominant light wavelengths (in nm for example) emitted by an array of the VCSELs. Here, VCSELs can achieve single mode output using elements with small apertures (e.g., about 2 μm or less). As an example, two graphs 540 and 542 show lasing spectra of a single aperture device and the various element size arrays, where N is the number of VCSEL elements in the array, W is power in watts, and d is the emitting VCSEL diameter of each element (also referred to as the VCSEL's aperture). The number of transverse modes (shown by each peak) decreases with element VCSEL diameter d, with the d=2 μm element emitting only a single transverse mode.

As to forming the illuminators with the VCSEL arrays, techniques to fabricate monolithically integrated multi-wavelength VCSELs include using patterned substrates or surface regrowth. By patterning the substrate with lithographically-defined structures prior to the growth of the VCSEL a gradient arises in surface temperature which results in a change of layer thickness which alters the lasing wavelength in accordance with the round-trip phase condition of the VCSEL cavity. Similarly, patterning of the substrate into a 2-D array of mesas of varying diameter gives rise to local chemical concentration gradients of gas species in a metal organic chemical vapor deposition (MOCVD) schemes and results in a change in the layer thickness of the VCSELs.

By one form, each VCSEL array (or multiple VCSEL arrays) shares the same stack of layers to form the individual VCSELs except for separate top DBR layers to emit light separately for each VCSEL. By other forms, each VCSEL array, and/or each VCSEL element, has its own separate stack of layers as with device 1100 (FIG. 11).

A single transverse mode VCSEL array based on a lithographic fabrication technique that enables good packing density and laser element uniformity, as well as lithographic VCSELs with multiple aperture sizes, and that could be used to enable emission of varying wavelengths for individual VCSELs is disclosed by J. Leshin, et al., “Lithographic VCSEL Array Multimode and Single Mode Sources for Sensing and 3D Imaging,” Proc. of SPIE Vol. 9854, 98540Y, 2016. doi: 10.1117/12.2222911.

Lithographic VCSELs have proven to be superior to oxide-aperture VCSELs (currently in production by most VCSEL suppliers) in numerous properties, most notably for small sizes. Such benefits include high power conversion efficiency and low thermal resistance, increased reliability, as well as stable single transverse mode output. Achievements in improved beam quality and spectral control allow these lithographic arrays to avoid the ‘donut’ mode pattern seen in arrays made with larger VCSEL elements.

Referring to FIG. 5C, a meta illuminator 550 has a lithographic VCSEL array 552 formed of individual VCSELs 554 on a substrate 556 and formed by using the processes mentioned above. The VCSELs may be 2 μm diameter (or VCSEL aperture) single transverse mode VCSEL elements spaced 4 μm center-to-center. The VCSEL elements have high uniformity in their size and operation.

In order to construct the VCSEL array with the metalayer, a method of forming the VCSEL array also may comprise each VCSEL element in the array having its own metalayer built above or layered onto the VCSEL as with VCSEL 1100 to produce the desired batwing far-field radiation pattern or other desired radiation patterns depending on the applications. The VCSEL light wavelength λ, used to dimension the metalayer on an individual VCSEL may be the specific wavelength of the particular VCSEL the metalayer is on, but otherwise may be some combination value such as the median, average (or dominant), or other value of wavelength related to the array of VCSELs.

Referring now to FIGS. 19-22, and as mentioned, by using a VCSEL as the illumination source, the system may improve ambient light rejection at the sensor (or camera) as well as reduce optical crosstalk in hybrid RGB-IR cameras. The VCSEL may be tuned to have a narrower wavelength than an LED which may allow for a reduction in the passband of the IR bandpass filter.

Referring to FIG. 19, a bandpass filter wavelength graph 1900 illustrates an example passband tuned for an LED source to compare to a VCSEL source of graph 2000 (FIG. 20). The graph has wavelength in nm along the horizontal axis and relative gain or energy along the vertical axis, where 1.0 is entirely passed through and 0.0 is entirely blocked with a transition in between the two states. IRBPF_0 is the IR bandpass wavelengths of received light permitted to pass a filter at 0 degrees (or optical center/axis of the camera viewing angle), while IRBPF_30 is the IR bandpass wavelengths of received light permitted to pass a filter at 30 degrees (or near the outer edge) of the camera viewing angle. Each of the two angles has a separate filter or is treated as having a separate filter. The 2800K is the graph of ambient light (in color temperature about 2800 Kelvins), Sensor QE refers to the quantum efficiency of the detector, and LED left and right refer to the worst case device to device and temperature shift of the center wavelength of the LED compared to the nominal center wavelength of the LED. To accommodate the change in transmission characteristics as a function of the angle of incidence, as well as the tolerances of the LED, the passband is relatively wide, which undesirably enables a significant amount of the 2800K illumination to enter the system. Here, this filter shows a passband of about 60 nm wide, and has been known to be up to 100 nm or even wider.

Referring to FIG. 20, graph 2000 illustrates an example bandpass filter for a VCSEL based illuminator. Here, the graph key is similar to that of graph 1900 except that a VCSEL 25 C and VCSEL 85 C (in ambient Celsius temperature) are used. Thus, in this example with the use of the VCSEL, the passband here may be about five times narrower than the passband with the LED solution, resulting in an increase of about five times in the ambient light that the system can manage (or reducing the amount of ambient light permitted to reach the sensor by 80%). Now, the passband is merely about 10-12 nm for example compared to the 60 nm passband for the LED, significantly reducing the amount of ambient light wavelengths that can pass through the filter. By other forms, it has been found that when an LED-based system has a passband of about 100 nm wide, the VCSEL-based system may use a BPF that has a passband of about 20 nm wide, and by another form about 20 nm wide or less, such as 10-12 nm wide.

Referring to FIG. 21, in addition to ambient light rejection, the bandpass filter may deliver improvements in the color quality as some NIR energy will leak into the RGB channels for the RGB-IR cameras. Graph 2100 illustrates an example system response to LED light, and provides the response for each of the RGB channels for both a filter at the 0 degree position and a filter at the 30 degree position of the camera viewing angle for each color channel. The highlighted energy (as shown encircled in graph 2100) in the NIR band may corrupt the colors. In some implementations, it may be partially removed by post processing. The crosstalk compensation, however, may increase noise and reduce SNR, which may be challenging (e.g., cause interference) in low light environments, especially when incandescent light is present. Here, the cross talk spans about 104 nm with a gain up to about 4.

Referring to FIG. 22, a graph 2200 illustrates the crosstalk reduction that may be enabled by the filter arranged for receiving light from the VCSEL. Both the wavelengths affected and the gain are reduced compared to that on the LED graph 2100. Now the cross-talk merely spans about 47 nm with a gain up to about 3, which significantly and desirably increases the SNR.

Such techniques and systems may be plausible if the size and cost of the VCSEL illuminator, including optics needed to manage the speckle and illumination pattern, may be managed. It should be noted, however, that the VCSEL still may be used for better emission control, and in turn ambient light interference reduction, with or without adding a metalayer described above.

As to LEDs, by one other alternative, it should be noted that providing the metalayer producing the batwing radiation pattern over a different light source other than the VCSEL, such as the LED, will still provide the benefits of the reduced (or valley) light intensity near 0 degrees and the increased peak light intensities at the outer edge of the image viewing emission angle (20-25 degrees in the above examples but which may change depending on the application) to provide a more even light intensity across an image to increase the SNR at the edges and corners of the image and improved image quality. Of course, such a configuration may forego the improvements in ambient light blockage at the sensor and energy efficiency at the light source provided by the VCSEL. When an LED is used instead of the VCSEL, the LED may still be an IR emitter, and by one example, at about 850 nm wavelength.

In addition, any one or more of the operations represented by the processes, devices, or explanations in FIGS. 1-22 may be undertaken in response to instructions provided by one or more computer program products. Such program products may include signal bearing media providing instructions that, when executed by, for example, a processor, may provide the functionality described herein. The computer program products may be provided in any form of one or more machine-readable media. Thus, for example, a processor including one or more processor core(s) may undertake one or more of the operations of the example processes herein in response to program code and/or instructions or instruction sets conveyed to the processor by one or more computer or machine-readable media. In general, a machine-readable medium may convey software in the form of program code and/or instructions or instruction sets that may cause any of the devices and/or systems to perform as described herein. The machine or computer readable media may be a non-transitory article or medium, such as a non-transitory computer readable medium, and may be used with any of the examples mentioned above or other examples except that it does not include a transitory signal per se. It does include those elements other than a signal per se that may hold data temporarily in a “transitory” fashion such as RAM and so forth.

As used in any implementation described herein, the term “module” refers to any combination of software logic and/or firmware logic configured to provide the functionality described herein. The software may be embodied as a software package, code and/or instruction set, and/or firmware that stores instructions executed by programmable circuitry. The modules may, collectively or individually, be embodied for implementation as part of a larger system, for example, an integrated circuit (IC), system on-chip (SoC), and so forth.

As used in any implementation described herein except where specifically described above, the term “logic unit” refers to any combination of firmware logic and/or hardware logic configured to provide the functionality described herein. The “hardware”, as used in any implementation described herein, may include, for example, singly or in any combination, hardwired circuitry, programmable circuitry, state machine circuitry, and/or firmware that stores instructions executed by programmable circuitry. The logic units may, collectively or individually, be embodied as circuitry that forms part of a larger system, for example, an integrated circuit (IC), system on-chip (SoC), and so forth. For example, a logic unit may be embodied in logic circuitry for the implementation firmware or hardware of the systems discussed herein. Further, one of ordinary skill in the art will appreciate that operations performed by hardware and/or firmware may also utilize a portion of software to implement the functionality of the logic unit.

As used in any implementation described herein, the term “engine” and/or “component” may refer to a module or to a logic unit, as these terms are described above. Accordingly, the term “engine” and/or “component” may refer to any combination of software logic, firmware logic, and/or hardware logic configured to provide the functionality described herein. For example, one of ordinary skill in the art will appreciate that operations performed by hardware and/or firmware may alternatively be implemented via a software module, which may be embodied as a software package, code and/or instruction set, and also appreciate that a logic unit may also utilize a portion of software to implement its functionality.

Referring to FIG. 23, an example image processing system 2300 is arranged in accordance with at least some implementations of the present disclosure. In various implementations, the example image processing system 2300 may have an imaging device 2302 to form or receive captured image data, and a projector unit 2306 to emit light to be reflected from objects and captured by the imaging device 2302. This can be implemented in various ways. Thus, in one form, the image processing system 2300 may be a digital camera or other image capture device (such as a dedicated camera), and imaging device 2302, in this case, may be the camera hardware and camera sensor software, module, or component 2310, while the projector unit 2306 is the projector hardware including a light source with a metalayer 2308 as described above, and may have projector software, modules or components as well. In other examples, image processing device 2300 may be a multi-purpose electronic device, such as on a smartphone or laptop for example, and may have an imaging device 2302, that includes or may be a camera, and the projector unit 2306. In either case, logic modules 2304 may communicate remotely with, or otherwise may be communicatively coupled to, the imaging device 2302 and projector unit 2306 for further processing of the image data.

Also in either case, such technology may include a camera such as a digital camera system, a dedicated camera device, or an imaging phone, whether a still picture or video camera or some combination of both. This may include a light projection and camera system such as a face detection, iris detection, or detection of other parts on a person to authorize an action or access for that person. Such a system may be provided on a multi-purpose computing device for access to that device, files on that device, or access to other objects, or could be part of a dedicated access authorization system such as a door or safe lock. Other forms for the image processing device 2300 may include a camera sensor-type imaging device or the like (for example, a webcam or webcam sensor or other complementary metal-oxide-semiconductor-type image sensor (CMOS)), with or without the use of a (RGB) depth camera and/or microphone-array to locate who is speaking. The camera sensor may also support other types of electronic shutters, such as global shutter in addition to, or instead of, rolling shutter, and many other shutter types. In other examples, an RGB-Depth camera may be used in addition to or in the alternative to a camera sensor. This may include an RGB-IR stereo camera.

In one form, imaging device 2302 may include camera hardware and optics including one or more sensors as well as auto-focus, zoom, aperture, ND-filter, auto-exposure, flash (if not provided by projector unit 2306), and actuator controls. These controls may be part of the sensor module or component 2310 for operating the sensor. The sensor component 2310 may be part of the imaging device 2302, or may be part of the logical modules 2304 or both. Such sensor component can be used to generate images for a viewfinder and take still pictures or video. The sensor component 2310 may be arranged to sense IR light, RGB light, or both. A bandpass filter (BPF) unit 2312 may provide filters for IR light, RGB light (such as with a Bayer color filter), or both as well. The imaging device 2302 also may have a lens, an analog amplifier, an A/D converter, an IR module 2314, optionally an RGB module 2316, and other components to convert incident light into a digital signal, the like, and/or combinations thereof, and provide statistical signals and data desired for analysis of an IR image for example (which may or may not include a computed SNR or the signals for another application to compute the SNR). The digital signal also may be referred to as the raw image data herein.

The projector unit 2306 may have those components necessary to operate the light source and metalayer, whether the light source is an IR VCSEL, IR LED, or other type of light source to emit IR or another type of light. Thus, the projector unit 2306 may include circuitry to control the power fed to the light source 2308 as well as one or more clock circuits to indicate when to turn the light source on and off. The light source may include an LED, VCSEL, or one or more arrays of VCSELs by the above examples. The projection module 2306 also may include other light sources, such as for the camera flash, or to provide additional types of light than IR.

In the illustrated example, the logic modules 2304 may include a camera control unit 2304 that manages the various general operations of the imaging device 2302 such as turning the camera on and off and transmits data from the imaging device, a light projection control 2322 that controls the power and lighting circuits of the projector unit 2306, an image capture unit 2324 that has a raw data handling unit 2326 that performs pre-processing on received image data, and then other image processing applications 2328 that process the image data for various purposes such as object detection including face or iris detection, eye tracking, image warping or augmentation, depth detection operations, and so forth. The applications 2328 also may include applications that compute and/or use the SNRs to analyze IR images, and if the SNR is not already computed or signal provided by the IR module 2314 for example. Otherwise, the IR module 2314

The image processing system 2300 may have one or more of processors 2330 which may include a dedicated image signal processor (ISP) 2332 such as the Intel Atom, memory stores 2344 with RAM, cache, and/or other memory types, one or more displays 2334, encoder 2348, and antenna 2340. In one example implementation, the image processing system 2300 may have the display 2334, at least one processor 2330 communicatively coupled to the display, at least one memory 2344 communicatively coupled to the processor, and having a buffer 2346 by one example for storing image data and other data related to projector unit 2306 and/or imaging device 2302. The encoder 2348 and antenna 2340 may be provided to compress the modified image date for transmission to other devices that may display or store the image. It will be understood that the image processing system 2300 may also include a decoder (or encoder 2348 may include a decoder) to receive and decode image data for processing by the system 2300. Otherwise, the processed image 2342 may be displayed on display 2334 or stored in memory 2344. As illustrated, any of these components may be capable of communication with one another and/or communication with portions of logic modules 2304, projector unit 2306, and/or imaging device 2302. Thus, processors 2330 may be communicatively coupled to the imaging device 2302, projector unit 2306, and the logic modules 2304 for operating those components. By one approach, although image processing system 2300, as shown in FIG. 23, may include one particular set of blocks or actions associated with particular components, units, or modules, these blocks or actions may be associated with different components, units, or modules than the particular component, unit, or module illustrated here.

Referring to FIG. 24, an example system 2400 in accordance with the present disclosure operates one or more aspects of the image processing systems described herein and may operate or include system 2300. It will be understood from the nature of the system components described below that such components may be associated with, or used to operate, certain part or parts of the image processing system described above. In various implementations, system 2400 may be a media system although system 2400 is not limited to this context. For example, system 2400 may be incorporated into a digital still camera, digital video camera, mobile device with camera or video functions such as an imaging phone, webcam, personal computer (PC), laptop computer, ultra-laptop computer, tablet, touch pad, portable computer, handheld computer, palmtop computer, personal digital assistant (PDA), cellular telephone, combination cellular telephone/PDA, television, smart device (e.g., smart phone, smart tablet or smart television), mobile internet device (MID), messaging device, data communication device, dedicated access authorization device, physical lock device, face login device, object detection device, and so forth.

In various implementations, system 2400 includes a platform 2402 coupled to a display 2420. Platform 2402 may receive content from a content device such as content services device(s) 2430 or content delivery device(s) 2440 or other similar content sources. A navigation controller 2450 including one or more navigation features may be used to interact with, for example, platform 2402 and/or display 2420. Each of these components is described in greater detail below.

In various implementations, platform 2402 may include any combination of a chipset 2405, processor 2410, memory 2412, storage 2414, graphics subsystem 2415, applications 2416 and/or radio 2418. Chipset 2405 may provide intercommunication among processor 2410, memory 2412, storage 2414, graphics subsystem 2415, applications 2416 and/or radio 2418. For example, chipset 2405 may include a storage adapter (not depicted) capable of providing intercommunication with storage 2414.

Processor 2410 may be implemented as a Complex Instruction Set Computer (CISC) or Reduced Instruction Set Computer (RISC) processors; x86 instruction set compatible processors, multi-core, or any other microprocessor or central processing unit (CPU). In various implementations, processor 2410 may be dual-core processor(s), dual-core mobile processor(s), and so forth.

Memory 2412 may be implemented as a volatile memory device such as, but not limited to, a Random Access Memory (RAM), Dynamic Random Access Memory (DRAM), or Static RAM (SRAM).

Storage 2414 may be implemented as a non-volatile storage device such as, but not limited to, a magnetic disk drive, optical disk drive, tape drive, an internal storage device, an attached storage device, flash memory, battery backed-up SDRAM (synchronous DRAM), and/or a network accessible storage device. In various implementations, storage 2414 may include technology to increase the storage performance enhanced protection for valuable digital media when multiple hard drives are included, for example.

Graphics subsystem 2415 may perform processing of images such as still or video for display. Graphics subsystem 2415 may be a graphics processing unit (GPU) or a visual processing unit (VPU), for example. An analog or digital interface may be used to communicatively couple graphics subsystem 2415 and display 2420. For example, the interface may be any of a High-Definition Multimedia Interface, Display Port, wireless HDMI, and/or wireless HD compliant techniques. Graphics subsystem 2415 may be integrated into processor 2410 or chipset 2405. In some implementations, graphics subsystem 2415 may be a stand-alone card communicatively coupled to chipset 2405.

The graphics and/or video processing techniques described herein may be implemented in various hardware architectures. For example, graphics and/or video functionality may be integrated within a chipset. Alternatively, a discrete graphics and/or video processor may be used. As still another implementation, the graphics and/or video functions may be provided by a general purpose processor, including a multi-core processor. In further implementations, the functions may be implemented in a consumer electronics device.

Radio 2418 may include one or more radios capable of transmitting and receiving signals using various suitable wireless communications techniques. Such techniques may involve communications across one or more wireless networks. Example wireless networks include (but are not limited to) wireless local area networks (WLANs), wireless personal area networks (WPANs), wireless metropolitan area network (WMANs), cellular networks, and satellite networks. In communicating across such networks, radio 818 may operate in accordance with one or more applicable standards in any version.

In various implementations, display 2420 may include any television type monitor or display. Display 2420 may include, for example, a computer display screen, touch screen display, video monitor, television-like device, and/or a television. Display 2420 may be digital and/or analog. In various implementations, display 2420 may be a holographic display. Also, display 2420 may be a transparent surface that may receive a visual projection. Such projections may convey various forms of information, images, and/or objects. For example, such projections may be a visual overlay for a mobile augmented reality (MAR) application. Under the control of one or more software applications 2416, platform 2402 may display user interface 2422 on display 2420.

In various implementations, content services device(s) 2430 may be hosted by any national, international and/or independent service and thus accessible to platform 2402 via the Internet, for example. Content services device(s) 2430 may be coupled to platform 2402 and/or to display 2420. Platform 2402 and/or content services device(s) 2430 may be coupled to a network 2460 to communicate (e.g., send and/or receive) media information to and from network 2460. Content delivery device(s) 2440 also may be coupled to platform 2402 and/or to display 2420.

In various implementations, content services device(s) 2430 may include a cable television box, personal computer, network, telephone, Internet enabled devices or appliance capable of delivering digital information and/or content, and any other similar device capable of unidirectionally or bidirectionally communicating content between content providers and platform 2402 and/display 2420, via network 2460 or directly. It will be appreciated that the content may be communicated unidirectionally and/or bidirectionally to and from any one of the components in system 2400 and a content provider via network 2460. Examples of content may include any media information including, for example, video, music, medical and gaming information, and so forth.

Content services device(s) 2430 may receive content such as cable television programming including media information, digital information, and/or other content. Examples of content providers may include any cable or satellite television or radio or Internet content providers. The provided examples are not meant to limit implementations in accordance with the present disclosure in any way.

In various implementations, platform 2402 may receive control signals from navigation controller 2450 having one or more navigation features. The navigation features of controller 2450 may be used to interact with user interface 2422, for example. In implementations, navigation controller 2450 may be a pointing device that may be a computer hardware component (specifically, a human interface device) that allows a user to input spatial (e.g., continuous and multi-dimensional) data into a computer. Many systems such as graphical user interfaces (GUI), and televisions and monitors allow the user to control and provide data to the computer or television using physical gestures.

Movements of the navigation features of controller 2450 may be replicated on a display (e.g., display 2420) by movements of a pointer, cursor, focus ring, or other visual indicators displayed on the display. For example, under the control of software applications 2416, the navigation features located on navigation controller 2450 may be mapped to virtual navigation features displayed on user interface 2422, for example. In implementations, controller 2450 may not be a separate component but may be integrated into platform 2402 and/or display 2420. The present disclosure, however, is not limited to the elements or in the context shown or described herein.

In various implementations, drivers (not shown) may include technology to enable users to instantly turn on and off platform 2402 like a television with the touch of a button after initial boot-up, when enabled, for example. Program logic may allow platform 2402 to stream content to media adaptors or other content services device(s) 2430 or content delivery device(s) 2440 even when the platform is turned “off.” In addition, chipset 2405 may include hardware and/or software support for 8.1 surround sound audio and/or high definition (7.1) surround sound audio, for example. Drivers may include a graphics driver for integrated graphics platforms. In implementations, the graphics driver may comprise a peripheral component interconnect (PCI) Express graphics card.

In various implementations, any one or more of the components shown in system 2400 may be integrated. For example, platform 2402 and content services device(s) 2430 may be integrated, or platform 2402 and content delivery device(s) 2440 may be integrated, or platform 2402, content services device(s) 2430, and content delivery device(s) 2440 may be integrated, for example. In various implementations, platform 2402 and display 2420 may be an integrated unit. Display 2420 and content service device(s) 2430 may be integrated, or display 2420 and content delivery device(s) 2440 may be integrated, for example. These examples are not meant to limit the present disclosure.

In various implementations, system 2400 may be implemented as a wireless system, a wired system, or a combination of both. When implemented as a wireless system, system 2400 may include components and interfaces suitable for communicating over a wireless shared media, such as one or more antennas, transmitters, receivers, transceivers, amplifiers, filters, control logic, and so forth. An example of wireless shared media may include portions of a wireless spectrum, such as the RF spectrum and so forth. When implemented as a wired system, system 2400 may include components and interfaces suitable for communicating over wired communications media, such as input/output (I/O) adapters, physical connectors to connect the I/O adapter with a corresponding wired communications medium, a network interface card (NIC), disc controller, video controller, audio controller, and the like. Examples of wired communications media may include a wire, cable, metal leads, printed circuit board (PCB), backplane, switch fabric, semiconductor material, twisted-pair wire, co-axial cable, fiber optics, and so forth.

Platform 2402 may establish one or more logical or physical channels to communicate information. The information may include media information and control information. Media information may refer to any data representing content meant for a user. Examples of content may include, for example, data from a voice conversation, videoconference, streaming video, electronic mail (“email”) message, voice mail message, alphanumeric symbols, graphics, image, video, text and so forth. Data from a voice conversation may be, for example, speech information, silence periods, background noise, comfort noise, tones and so forth. Control information may refer to any data representing commands, instructions or control words meant for an automated system. For example, control information may be used to route media information through a system, or instruct a node to process the media information in a predetermined manner. The implementations, however, are not limited to the elements or in the context shown or described in FIG. 24.

Referring to FIG. 25, a small form factor device 2500 is one example of the varying physical styles or form factors in which systems 2300 or 2400 may be embodied. By this approach, device 1200 may be implemented as a mobile computing device having wireless capabilities. A mobile computing device may refer to any device having a processing system and a mobile power source or supply, such as one or more batteries, for example.

As described above, examples of a mobile computing device may include a digital still camera, digital video camera, mobile devices with camera or video functions such as imaging phones, webcam, personal computer (PC), laptop computer, ultra-laptop computer, tablet, touch pad, portable computer, handheld computer, palmtop computer, personal digital assistant (PDA), cellular telephone, combination cellular telephone/PDA, television, smart device (e.g., smart phone, smart tablet or smart television), mobile internet device (MID), messaging device, data communication device, and so forth.

Examples of a mobile computing device also may include computers that are arranged to be worn by a person, such as a wrist computer, finger computer, ring computer, eyeglass computer, belt-clip computer, arm-band computer, shoe computers, clothing computers, and other wearable computers. In various implementations, for example, a mobile computing device may be implemented as a smart phone capable of executing computer applications, as well as voice communications and/or data communications. Although some implementations may be described with a mobile computing device implemented as a smart phone by way of example, it may be appreciated that other implementations may be implemented using other wireless mobile computing devices as well. The implementations are not limited in this context.

As shown in FIG. 25, device 2500 may include a housing with a front 2501 and a back 2502. Device 2500 includes a display 2504, an input/output (I/O) device 2506, and an integrated antenna 2508. Device 2500 also may include navigation features 2512. I/O device 2506 may include any suitable I/O device for entering information into a mobile computing device. Examples for I/O device 2506 may include an alphanumeric keyboard, a numeric keypad, a touch pad, input keys, buttons, switches, microphones, speakers, voice recognition device and software, and so forth. Information also may be entered into device 2500 by way of microphone 2514, or may be digitized by a voice recognition device. As shown, device 2500 may include a camera 2505 (e.g., including at least one lens, aperture, and imaging sensor) and a flash 2510 integrated into back 2502 (or elsewhere) of device 2500. The implementations are not limited in this context.

Various forms of the devices and processes described herein may be implemented using hardware elements, software elements, or a combination of both. Examples of hardware elements may include processors, microprocessors, circuits, circuit elements (e.g., transistors, resistors, capacitors, inductors, and so forth), integrated circuits, application specific integrated circuits (ASIC), programmable logic devices (PLD), digital signal processors (DSP), field programmable gate array (FPGA), logic gates, registers, semiconductor device, chips, microchips, chip sets, and so forth. Examples of software may include software components, programs, applications, computer programs, application programs, system programs, machine programs, operating system software, middleware, firmware, software modules, routines, subroutines, functions, methods, procedures, software interfaces, application program interfaces (API), instruction sets, computing code, computer code, code segments, computer code segments, words, values, symbols, or any combination thereof. Determining whether an implementation is implemented using hardware elements and/or software elements may vary in accordance with any number of factors, such as desired computational rate, power levels, heat tolerances, processing cycle budget, input data rates, output data rates, memory resources, data bus speeds and other design or performance constraints.

One or more aspects of at least one implementation may be implemented by representative instructions stored on a machine-readable medium which represents various logic within the processor, which when read by a machine causes the machine to fabricate logic to perform the techniques described herein. Such representations, known as “IP cores” may be stored on a tangible, machine readable medium and supplied to various customers or manufacturing facilities to load into the fabrication machines that actually make the logic or processor.

While certain features set forth herein have been described with reference to various implementations, this description is not intended to be construed in a limiting sense. Hence, various modifications of the implementations described herein, as well as other implementations, which are apparent to persons skilled in the art to which the present disclosure pertains are deemed to lie within the spirit and scope of the present disclosure.

The following examples pertain to further implementations.

By one example, a light emitting device comprises: an illuminator comprising at least one light source having a stack of layers comprising a layer with a light emitting surface; and a metalayer disposed at the stack of layers to receive light from the light emitting surface, and having a plurality of spaced light scattering posts to receive light from the light emitting surface and change the direction of the light from the direction of the light received from the light emitting surface, wherein the light source and metalayer are arranged to cooperatively form a predetermined far-field light intensity radiation pattern.

By another implementation, the light emitting device also comprises wherein the far-field radiation pattern is shaped to increase a uniformity of light intensity on a resulting image formed from reflecting the emitted light on an object; wherein the far-field radiation pattern is shaped in a batwing shape comprising a lower light intensity valley part between two peaks of light intensity parts along the batwing radiation pattern; wherein the light scattering posts are sized, shaped and spaced from each other in both distance and direction to form the lower intensity part and the two peaks of the batwing radiation pattern; wherein the at least one light source is a vertical-cavity surface emitting laser (VCSEL); wherein the light source is arranged to emit infra-red or near-infra-red light; wherein the metalayer is formed of at least one of: silicon-germanium with germanium content less than 20%, TiO_(x) where x<2, and TiO_(x) where 1<x<2; wherein the widths or diameters of the posts vary from individual post to individual post and along the metalayer, wherein light emitted has a wavelength of λ, wherein the widths or diameters vary by about λ/10 to about λ/4 in a plane of the metalayer, wherein the posts are spaced in a hexagonal lattice in top view at a distance of about λ/4 to about λ/2 to each other; wherein the posts are cylindrical in top view, wherein one of: (A) the at least one light source is at least one array of VCSELs wherein each or individual VCSELs of the array emit a different wavelength, and (B) the at least one light source is a plurality of arrays of the VCSELs, wherein each array has a dominant wavelength different from the dominant wavelength of at least one other array.

By yet another implementation, a system for image processing, comprises a light emitting device comprising an infra-red (IR) or near-infra-red (NIR) illuminator comprising at least one vertical-cavity surface emitting laser (VCSEL) and having a stack of layers comprising a layer with a light emitting surface; and a metalayer disposed at the stack of layers and having a plurality of spaced light scattering posts to receive light from the light emitting surface and emit the light in a different direction than the direction received from the light emitting surface, wherein the VCSEL and metalayer are arranged to cooperatively form a predetermined far-field light intensity radiation pattern; and an imaging device to receive reflected light emitted by the light emitting device comprising: a sensor for sensing the received light; and a band pass filter limiting the wavelengths of the light that reaches the sensor.

By another example, the system comprises wherein the passband of the filter has a width from cutoff to cutoff at about 20 nm or less; and wherein the VCSEL establishes a fall-off of the outer wings of the batwing that reaches 0 light intensity at less than about 45 degrees from a 0 degree central optical axis of the light emitting device.

By a further example, a method of emitting light to capture images comprises method of emitting light to capture images, comprising: emitting IR or NIR light from a vertical-cavity surface emitting laser (VCSEL); redirecting the light from the VCSEL by a metalayer disposed on the VCSEL; and emitting, by the metalayer, the light in a far-field batwing radiation pattern having a shape at least partially formed depending on a structure of posts on the metalayer.

The method also may include emitting light from posts on the metalayer sized, shaped, and spaced in both direction and distance to form the batwing radiation pattern; wherein the far-field batwing radiation pattern has two peaks at about 20% greater relative light intensity than the lowest point of a valley between the two peaks, wherein the batwing has upper peaks at about an outer edge emission angle that has light used to form outer edges of a resulting image; emitting light from one of: (A) at least one array of the VCSELs comprising emitting a different wavelength from each or individual VCSELs of the array; and emitting light with at least about 1 nm or less difference in wavelength from VCSEL to VCSEL in the same array; or (B) emitting light from multiple arrays of the VCSELs comprising emitting a different dominant wavelength from each or individual arrays; and emitting light with about 1 nm or less difference in dominant wavelength from VCSEL array to VCSEL array.

By a further example, a method of forming a light emitting device comprises forming an infra-red (IR) or near-infra-red (NIR) illuminator comprising a vertical-cavity surface emitting laser (VCSEL) having a layer with a light emitting surface; forming a metalayer having a plurality of spaced light scattering posts disposed to receive light from the light emitting surface and emit the light in a different direction than the direction received from the light emitting surface; and arranging the VCSEL and metalayer to cooperatively form a far-field batwing radiation pattern of light emission comprising a lower light intensity valley part between two peaks of light intensity parts along the batwing radiation pattern.

The method also may be comprising forming the posts with a size, shape, and spacing in both distance and direction to emit light from the posts to form the batwing radiation pattern; arranging the posts to emit light with a wavelength of λ, and the method comprising forming the posts with: a curvalinear shape, a width or diameter of about λ/10 to about λ/4 distributed non-uniformly on the metalayer, a height of the posts of at most about λ/2, and a hexagonal lattice spacing at a center distance of about λ/4 to about λ/2 from post to post; forming the posts with diameters or widths to vary on a surface of the metalayer in order to form the batwing radiation pattern; wherein the posts are formed of TiO_(x) where 1<x<2; forming one of (1) at least one array of VCSELs, wherein each or individual VCSELs in the same array emit light at a different wavelength, and (2) multiple arrays of VCSELs, wherein each VCSEL array is arranged to emit light at a different dominant wavelength.

In a further example, at least one machine readable medium may include a plurality of instructions that in response to being executed on a computing device, causes the computing device to perform the method according to any one of the above examples.

In a still further example, an apparatus may include means for performing the methods according to any one of the above examples.

The above examples may include specific combination of features. However, the above examples are not limited in this regard and, in various implementations, the above examples may include undertaking only a subset of such features, undertaking a different order of such features, undertaking a different combination of such features, and/or undertaking additional features than those features explicitly listed. For example, all features described with respect to any example methods herein may be implemented with respect to any example apparatus, example systems, and/or example articles, and vice versa. 

What is claimed is:
 1. A light-emitting device comprising: an illuminator comprising at least one light source having a stack of layers comprising a layer with a light emitting surface; and a metalayer disposed at the stack of layers to receive light from the light emitting surface, and having a plurality of spaced light scattering posts to receive light from the light emitting surface and change the direction of the light from the direction of the light received from the light emitting surface, wherein the light source and metalayer are arranged to cooperatively form a predetermined far-field light intensity radiation pattern.
 2. The device of claim 1 wherein the far-field radiation pattern is shaped to increase a uniformity of light intensity on a resulting image formed from reflecting the emitted light on an object.
 3. The device of claim 1 wherein the far-field radiation pattern is shaped in a batwing shape comprising a lower light intensity valley part between two peaks of light intensity parts along the batwing radiation pattern.
 4. The system of claim 3 wherein the light scattering posts are sized, shaped and spaced from each other in both distance and direction to form the lower intensity part and the two peaks of the batwing radiation pattern.
 5. The device of claim 1 wherein the at least one light source is a vertical-cavity surface emitting laser (VCSEL).
 6. The device of claim 1 wherein the at least one light source is a light emitting diode (LED).
 7. The device of claim 1 wherein the light source is arranged to emit infra-red or near-infra-red light.
 8. The device of claim 1 wherein the metalayer is formed of at least one of: silicon-germanium with germanium content less than 20%, TiO_(x) where x<2, and TiO_(x) where 1<x<2.
 9. The device of claim 1 wherein the widths or diameters of the posts vary from individual post to individual post and along the metalayer.
 10. The device of claim 9 wherein light emitted has a wavelength of λ, and wherein the widths or diameters vary by about λ/10 to about λ/4 in a plane of the metalayer.
 11. The device of claim 1 wherein light emitted has a wavelength of λ, and wherein the posts are spaced in a hexagonal lattice in top view at a distance of about λ/4 to about λ/2 to each other.
 12. The device of claim 1 wherein the posts are cylindrical in top view.
 13. The device of claim 1 wherein the at least one light source is at least one array of VCSELs wherein each or individual VCSELs of the array emit a different wavelength.
 14. The device of claim 1 wherein the at least one light source is a plurality of arrays of the VCSELs, wherein each array has a dominant wavelength different from the dominant wavelength of at least one other array.
 15. A system for image processing, comprising: a light emitting device comprising: an infra-red (IR) or near-infra-red (NIR) illuminator comprising at least one vertical-cavity surface emitting laser (VCSEL) and having a stack of layers comprising a layer with a light emitting surface; and a metalayer disposed at the stack of layers and having a plurality of spaced light scattering posts to receive light from the light emitting surface and emit the light in a different direction than the direction received from the light emitting surface, wherein the VCSEL and metalayer are arranged to cooperatively form a predetermined far-field light intensity radiation pattern; and an imaging device to receive reflected light emitted by the light emitting device comprising: a sensor for sensing the received light; and a band pass filter limiting the wavelengths of the light that reaches the sensor.
 16. The system of claim 15 wherein the passband of the filter has a width from cutoff to cutoff at about 20 nm or less.
 17. The system of claim 15 wherein the VCSEL establishes a fall-off of the outer wings of the batwing that reaches 0 light intensity at less than about 45 degrees from a 0 degree central optical axis of the light emitting device.
 18. A method of emitting light to capture images, comprising: emitting IR or NIR light from at least one vertical-cavity surface emitting laser (VCSEL); redirecting the light from the VCSEL by a metalayer disposed on the VCSEL; and emitting, by the metalayer, the light in a far-field batwing radiation pattern having a shape at least partially formed depending on a structure of posts on the metalayer.
 19. The method according to claim 18 comprising emitting light from posts on the metalayer sized, shaped, and spaced in both direction and distance to form the batwing radiation pattern.
 20. The method of claim 18 wherein the batwing has upper peaks at about an outer edge emission angle that has light used to form outer edges of a resulting image.
 21. The method of claim 18 comprising emitting light from at least one array of the VCSELs comprising emitting a different wavelength from each or individual VCSELs of the array.
 22. A method of forming a light emitting device comprising: forming an infra-red (IR) or near-infra-red (NIR) illuminator comprising at least one vertical-cavity surface emitting laser (VCSEL) having a layer with a light emitting surface; forming a metalayer having a plurality of spaced light scattering posts disposed to receive light from the light emitting surface and redirect the light; and arranging the VCSEL and metalayer to cooperatively form a far-field batwing radiation pattern of light emission comprising a lower light intensity valley part between two peaks of light intensity parts along the batwing radiation pattern.
 23. The method according to claim 22 comprising forming the posts with a size, shape, and spacing in both distance and direction to emit light from the posts to form the batwing radiation pattern.
 24. The method of claim 22 comprising arranging the posts to emit light with a wavelength of λ, and the method comprising forming the posts with: a curvalinear shape, a width or diameter of about λ/10 to about λ/4 distributed non-uniformly on the metalayer, a height of the posts of at most about λ/2, and a hexagonal lattice spacing at a center distance of about λ/4 to about λ/2 from post to post.
 25. The method of claim 22 comprising forming the posts with diameters or widths to vary on a surface of the metalayer in order to form the batwing radiation pattern. 